863 



JOURNAL OL- FORESTRY 



Yet, in these exceptional "red trees" and on the red part of the 

 heartwood of the latter case^ the marked acidity of the sap was notice- 

 able with litmus-paper. Therefore, it seems possible that, when the 

 darkening indirectly caused by the wound takes place while the tree 

 is standing or on first exposure to air after its felling, the acidity of 

 the sap and the amount of ammonia produced interfere in the phe- 

 nomenon in opposite directions, while the quantity of "particular sub- 

 stance" controls the intensity of the darkening to a large extent. 



VARIETY HYPOTHESIS OF BLACK TREE 



It seems to us that there may be in all probability many varieties or 

 forms among the forest trees of "Sugi" besides those varieties known 

 in horticulture, such as var. elcgans Mast., var. tincinafa S. et Z., 

 var. nana Fort., var. arancoriodes S. et Z., etc. But confusion of these 

 possible varieties or forms with "black tree" should be avoided. There 

 is no dififey-ence between the young trees of "red tree" and "black tree." 

 According to the reason already provided, all the heartwood can be 

 made to undergo darkening. As is well-known, "black wood" usually 

 deviates from "red wood" in the water content ; figures are given in 

 the following determinations of green materials. No. 8 is exceptional 

 (and will be discussed later). 



Table 8. 



Some ecologically different features attributed to "black tree" in 

 some localities are probably due to the wood's high water content. 

 A tendency to be relatively resistant to drying is sometimes noticed in 

 "black wood." As no distinct difiference in the stomata, so far as 

 their number and distribution are concerned, exists between "black" 

 and "red" trees, the marked increase in water content of "black wood" 



